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Loggings => HF Mystery Signals => Topic started by: housecat on March 17, 2017, 0601 UTC

Title: Alternating tones 13985
Post by: housecat on March 17, 2017, 0601 UTC

Heard on the Twente WebSDR, tuned in about 5:50Z Friday.  Two alternating tones centered on 13985khz.  At about 5:55Z it switched to a continuous pitch of the lower tone.  Continuous pitch is still going as of 6:00Z.  I'm never clear when to interpret something as a CW or as a carrier.

http://robp.meowr.net/stuff/unid_alt_tone_2017-03-17T05-48-16Z_13984.0kHz.wav (http://robp.meowr.net/stuff/unid_alt_tone_2017-03-17T05-48-16Z_13984.0kHz.wav)
(http://robp.meowr.net/stuff/alt_tone_unid.png)

Title: Re: Alternating tones 13985
Post by: Token on March 18, 2017, 0419 UTC

This is a frequency normally occupied by Russian military CIS 81-81 FSK.  CIS 81-81 on this frequency uses 500 Hz shift, and that matches the shift of this signal.  This is probably that modem in a test mode, alternating the two tones.

T!